The present invention relates to a technique of correcting and controlling with high accuracy a fuel injection quantity during transient operation when variably controlling valve timing, in an engine equipped with a variable valve timing mechanism.
Heretofore, in a fuel injection control of an engine for vehicle, a transient correction is performed so as to suppress a change in air-fuel ratio caused by a change in a wall flow amount of fuel during a transient operation.
Japanese Unexamined Patent Publication No. 11-218043 discloses that a port wall flow amount of injection fuel adhered to an intake port, a cylinder wall flow amount of fuel adhered to an inner wall of a cylinder, and the like are computed to set a fuel injection quantity with high accuracy even during a transient operation when these wall flow amounts are changed.
On the other hand, there has been proposed an engine equipped with a variable valve timing control mechanism that successively and variably changes the valve timing (opening and closing timing) of intake and exhaust valves by changing a rotation phase of a camshaft relative to a crankshaft (Japanese Unexamined Patent Publication 10-141022).
According to the engine equipped with the above-mentioned variable valve timing mechanism, the valve timing is changed accompanied by a change in operating condition during a transient operation, thus a valve overlap amount of the intake/exhaust valves is changed. Therefore, when controlling a fuel injection quantity during the transient operation, a change in valve overlap amount influences a wall flow amount, but conventionally, a transient correction amount is adjusted (set) according to the change in operating condition during the transient operation including the valve overlap amount change.
However, as mentioned above in the case where the transient correction amount is adjusted according to the change in operating condition during the transient operation including the change in valve overlap amount, it is impossible to cope with variations in transient characteristic of the valve timing. In other words, when the operating condition is changed under the same conditions, if a response characteristic of an actual valve timing to a target valve timing does not fall under an allowable limit of response characteristic during the transient correction amount is adjusted, the fuel injection quantity cannot be set well due to the deviation of valve overlap change characteristic, and thus the transient operating performance and the exhaust emission performance are deteriorated due to the deviation of air-fuel ratio.
The present invention has been achieved in view of the above-mentioned problem and has an object to accurately controlling a fuel injection quantity during a transient operation where the valve timing is changed, without being influenced by the dispersion of response characteristic of a variable valve timing mechanism.
In order to achieve the above-mentioned object, the present invention is constituted so that, in an engine equipped with a variable valve timing mechanism that variably controls the valve timing successively, when variably controlling the valve timing, a transient correction amount of fuel to be supplied to the engine is corrected based on a detection value of a valve overlap amount of intake/exhaust valves.
According to this constitution, even if variations exist in a response characteristic in the valve timing control, the transient correction amount can be corrected based on the detection value of the valve overlap amount of the intake/exhaust valves, thereby enabling to perform a correction corresponding to a response delay, thus realizing the satisfactory transition operating performance.
The other objects and features of the present invention will become understood from the following description with reference to the accompanying drawings.